Re: words in COMPWORDS vs. words in COMPREPLY

[Chet Ramey]

On 7/20/10 3:14 PM, Ben Pfaff wrote:
> I'm trying to learn how bash completion works, so that I can
> write completion functions for some utilities.
> 
> As an experiment, I wrote the following trivial completion.  It
> is intended to report that the completions for the current word
> are exactly the contents of the current word:
> 
>     _test () {
>         COMPREPLY=(${COMP_WORDS[COMP_CWORD]})
>     }
>     complete -F _test test
> 
> I expected that, with the above, typing "test", followed by a
> word, followed by <TAB>, would cause bash just to insert a space.
> This is often what happens, but I've found some exceptions that I
> do not yet understand.  For example, consider the following:
>     test x=
> 
> When I press <TAB>, I expected this to expand to:
>     test x=
> followed by a space.
> With Debian's bash 4.1-3 (on which bash --version reports
> "version 4.1.5(1)-release"), this actually expands as:
>     test x==
> followed by a space.
> 
> With Debian's bash 3.2-4 ("bash 3.2.39(1)-release"), this expands
> as:
>     test x=x=
> followed by a space.

Since `=' is one of the characters readline uses to break words for the
completer, ${COMP_WORDS[$COMP_CWORD]} expands to `='.  It's treated as
a separate word on the line.

One of the changes between bash-3.2 and bash-4.0 was to make the
programmable completion code use the same set of characters as readline
to break the line into words:

i.  The programmable completion code now uses the same set of characters as
    readline when breaking the command line into a list of words.

This explains the behavior difference between bash-3.2 and bash-4.1.

If you want to remove `=' from the set of characters used to break words
for completion, modify the COMP_WORDBREAKS variable.

Chet
-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/